Hydrometallurgy 198 (2020) 105507 Available online 22 October 2020 0304-386X/© 2020 Elsevier B.V. All rights reserved. Technical note A modified process for leaching of ilmenite and production of TiO 2 nanoparticles Vahid Kordzadeh-Kermani a, * , Mahin Schaffie a, b , Hassan Hashemipour Rafsanjani a, c , Mohammad Ranjbar b a Department of Chemical Engineering, Shahid Bahonar University of Kerman, Kerman, Iran b Mineral Industries Research Center, Shahid Bahonar University of Kerman, Kerman, Iran c Department of Chemical Engineering, Vali-e-Asr University of Rafsanjan, Rafsanjan, Iran A R T I C L E INFO Keywords: Nanostructure TiO 2 Ilmenite Hydrometallurgy Leaching EDTA ABSTRACT Titanium dioxide is an important material with a wide range of applications. Different methods and processes have been introduced and applied to produce pure TiO 2 from available titanium ores and mineral sources. This paper describes the production of nano-sized titanium dioxide (TiO 2 ) from ilmenite concentrate provided by the main Iranian Ilmenite processing complex. Ilmenite (FeTiO 3 ) concentrate was decomposed using (70% wt.) potassium hydroxide solution at 220 ◦ C and under air at atmospheric conditions. The decomposed product was leached using hydrochloric acid solution, and Ethylenediaminetetraacetic acid (EDTA) was applied for chelating and separating iron impurity from the leach solution. Ammonia solution was used for precipitation, and the anatase TiO 2 nanoparticles were produced in the following filtration, drying, and calcination processes. The water content of the filtrate solution was evaporated, and it was dried to produce a powdery product. The crystal phases of ilmenite, decomposed ilmenite, and the TiO 2 product were characterized by X-ray diffraction (XRD), and the chemical compositions of the ilmenite concentrate, products, and the filtrate were determined using inductively coupled plasma-optical emission spectrometry (ICP-OES). The morphological study of the decom- posed ilmenite and synthesized-TiO 2 was performed using scanning electron microscope (SEM) and field emis- sion scanning electron microscope (FESEM), respectively. The particle size measurement of the TiO 2 product was conducted using dynamic light scattering (DLS) method. The crystal system and lattice parameters were calculated by the Rietveld refinement method. The purity of the produced synthesized-TiO 2 was determined to be more than 90% with a mean particle size diameter of around 70 nm. The filtrate solution (as the main byproduct of the process) contained Fe-EDTA chelated complexes, sodium, potassium, and some other constituents that can be used in agricultural fertilizer production. 1. Introduction Titanium dioxide (TiO 2 ) in different crystal phases has attracted significant attention. It has been utilized in various applications such as pigment, semiconductor agent, and photocatalyst due to its remarkable index of refraction and the capability to adjust the surface area, pore size, and structure. The well known and most abundant raw material for the production of titanium dioxide is ilmenite (FeTiO 3 ). There are two main industrial methods to produce TiO 2 , namely, sulfate and chloride processes (L¨ of et al., 2020; Tian, 2019; Zhang et al., 2011). These pro- cesses consume high energy and produce high amounts of wastes. To date, various hydrometallurgical and pyrometallurgical processes were proposed for purifying ilmenite concentrates and removing impurities (Nguyen and Lee, 2018; Wang et al., 2018; Wu et al., 2013). In a novel energy-saving approach, ilmenite concentrates were mil- led with aluminum powder to produce an agglomerated mixture. The presence of aluminum in the mixture led to production of nascent hydrogen in the system during acid leaching that enhanced the leaching efficiency (Schirmer et al., 2020). Other researchers improved the Becher process by applying aeration and anthraquinone-based redox catalysts during processing of reduced ilmenite, which is led to pro- duction of high purity synthetic rutile and magnetic Fe 3 O 4 products (Xiang et al., 2020). In a solvent extraction route, Fe(III) and Ti(IV) were separated from * Corresponding author at: Department of Chemical Engineering, Shahid Bahonar University of Kerman, Kerman, Iran. E-mail addresses: kordzadeh2000@yahoo.com, v_kordzadeh@chemeng.iust.ac.ir (V. Kordzadeh-Kermani). Contents lists available at ScienceDirect Hydrometallurgy journal homepage: www.elsevier.com/locate/hydromet https://doi.org/10.1016/j.hydromet.2020.105507 Received 3 August 2019; Received in revised form 9 October 2020; Accepted 19 October 2020